The present invention relates generally to a diaphragm-type carburetor and more particularly to a fuel flow control device for a diaphragm-type carburetor.
In a conventional diaphragm-type carburetor, a fuel flow control valve opens and closes in response to the movement of a diaphragm to admit fuel into a fuel chamber and maintain fuel therein under a substantially constant pressure. To accomplish this, a lever is pivotably supported on a shaft within the fuel chamber. One end of the lever is biased and abutted against the diaphragm by means of a spring, and the other end of the lever engages a valve body of the flow control valve. FIG. 5 shows one such lever 55 of a conventional carburetor. The lever has a cut-out 80 at one end thereof to define a pair of left and right arms. The clearance between the arms is larger than the diameter of a circumferential engagement groove 72 (FIG. 2) formed in an outer surface of the valve body of the flow control valve. Undesirably, the lever can become disengaged from the groove 72 when the lever is in an inclined position, particularly, when a subassembly including the lever and the flow control valve body is mounted in the constant pressure fuel chamber of the carburetor.
An improved fuel flow control device of a diaphragm-type carburetor having a lever which can be easily coupled to a flow control valve body and cannot become disengaged from the flow control valve body in use and has a reliable and repeatable operational movement.
The fuel flow control device embodying the invention has a constant pressure fuel chamber defined in part by a fuel metering diaphragm with a pivotably mounted lever therein actuated by the diaphragm and coupled to a valve body so that it cannot become disengaged in use. One end of the lever is biased and abutted with the diaphragm preferably by a spring. The flow control valve body is operably connected to the other end of the lever for movement relative to a valve seat between open and closed positions to control fluid flow through an inlet passage leading to the constant pressure fuel chamber. The end of the lever coupled to the valve body preferably has a boss and a pair of arms extending perpendicular to the boss. A top plate having an opening is fitted on the lever on or between the pair of arms. The opening of the top plate is adapted to receive the valve body in the area of a circumferential engagement groove formed in the valve body. The top plate has a pair of spaced apart and generally opposed resilient hook pieces with a clearance or gap between them which is smaller then the diameter of the valve body in the area of the engagement groove. The hook pieces are at least somewhat flexible to permit the valve body to pass thereby into the opening in the top plate and are resilient so that they return to their unflexed position after the valve body passes to maintain the valve body in the opening. In this manner, unintended disengagement or separation of the lever and valve body is prevented in use of the carburetor.
In another form, the lever has a circumferentially continuous opening of a smaller diameter than an end portion of the valve body and slightly larger diameter than the valve body in the engagement groove. The lever is somewhat flexible and resilient in the area of the opening and flexes to permit the end portion of the valve body to pass thereby disposing the engagement groove in the opening. Thereafter, the flexed portion of the lever preferably returns sufficiently towards its unflexed orientation to prevent the end portion from passing thereby in use of the valve assembly. This prevents unintended separation of the lever and valve body.
Objects, features and advantages of this invention include providing a fuel flow control device which is easy to assembly, is easy to install in a carburetor, prevents separation of a lever and valve body in use, provides a smooth operation and movement of the valve body, is reliable, durable, of relatively simple design and economical manufacture and assembly and in service has a long useful life.